The FAA has proposed issuing an airworthiness directive applicable to numerous Piper Aircraft twin-engine airplanes, including Apaches, Aztecs, and Twin Comanches, superseding an existing AD that requires inspection of the heater exhaust extension, replacement of the extension as necessary, and overhaul of the combustion heater assembly because of a risk of carbon monoxide entering the cabin.

The proposed AD, applicable to all Piper Aircraft, Inc. Models PA-23, PA-23-160, PA-23-235, PA-23-250, PA-E23-250, and PA-30 airplanes, “would retain the inspection of the heater exhaust extension, with replacement of the extension as necessary, and remove the overhaul requirement of the combustion heater assembly,” according to a Notice of Proposed Rulemaking published by the agency March 2.

Comments will be accepted by the FAA on the proposed AD until April 17. AOPA encourages operators to submit comments as provided below, and share them, as well as any concerns about the proposal, with AOPA.

The FAA estimates that the proposed AD affects 1,950 airplanes, and will cost $85 per aircraft for inspection; $1,085 to replace the heater exhaust extension, if necessary; and an additional $85 to remove or disable the heater, if necessary.

After the original airworthiness directive, AD 69-13-03, was issued, the FAA proposed an AD applicable to Meggitt (Troy), Inc. combustion heaters that incorporates “corrective actions for the heater that contradict the overhaul requirement of AD 69-13-03,” the FAA said.

The FAA has no way of determining the number of airplanes that might need the corrective actions, and there are no heater exhaust extension replacement parts currently available, the agency said.

Comments may be submitted online or by mail by April 17 to U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. Please include “Docket No. FAA-2017-9157; Directorate Identifier 2016-CE-039-AD” at the beginning of your comments.